Spatial light modulators used in sequential color display systems are capable of projecting image details from media sources such as HDTV, DVD, and DVI. One common technique in projecting image details involves the use of a color. Light from a light source passes through a particularly colored segment of a color wheel and emerges as that color. This colored light illuminates the spatial light modulator and a portion of it is reflected onto a display screen based on the image detail to be displayed. In order to reproduce a full color image, the segments of the color wheel are of different colors so that as it spins the color of light that is reflected onto the display screen changes. The color wheel makes several revolutions for every frame of the image to be displayed. The number of revolutions made per frame depends, in part, on the number of segments in the color wheel.
Two common problems with display systems utilizing a single spatial light modulator are motion contouring (PWM artifacting) and color breakup (rainbow effect). Motion contouring appears as false contours that arise when the eye is tracking a moving object. The false contour may be a ghost image at sharp edges or an artificial contour in smoothly varying regions. The rainbow effect appears as a momentary flash of rainbow-like striping typically trailing bright objects when looking from one side of the screen to the other quickly, or when quickly looking away from the TV to an off-screen object.
One technique used for improving color breakup is to increase the refresh rate or the number of color cycles. This may be done by increasing the speed of the color wheel or increasing the number color segments for the color wheel (e.g., two segments of each color instead of one segment of each color). Unfortunately this increases the impact of motion contouring. Conversely, decreasing the refresh rate (e.g., slowing down the color wheel or decreasing the number of color segments for the color wheel) in order to improve motion contouring by allowing more time to deploy grey level for each color of the color wheel will increase the color separation.